Field of the Invention
The present invention relates to an imaging apparatus and an image coding apparatus for coding an image captured from a plurality of viewpoints.
Description of the Related Art
Conventionally, there is a method for generating an image at an arbitrary focal length, depth of field, and a viewpoint, using a multi-viewpoint image capturing an object from a plurality of viewpoints. Encoding (hereinafter coding) is then performed on the captured multi-viewpoint image, so that a data amount can be reduced. Such coded data can be recorded in a storage medium, or transferred to a server via a network.
Japanese Patent Application Laid-Open No. 9-0261653 discusses using inter-viewpoint prediction coding (hereinafter referred to as inter-viewpoint prediction) for coding the captured multi-viewpoint image. If the captured multi-viewpoint images are close to each other, there is correlation between each of the images. The inter-viewpoint prediction thus uses such correlation between the images. Japanese Patent Application Laid-Open No. 9-0261653 discusses capturing an object from a plurality of viewpoints employing a plurality of cameras, and acquiring the multi-viewpoint image. One of the viewpoints among the plurality of viewpoints is then set as a base viewpoint.
When coding the image captured from the viewpoint set as the base viewpoint, an image captured in the past from a viewpoint which is identical to the base viewpoint (hereinafter referred to as an identical viewpoint image) is used as a reference image. On the other hand, if the image acquired by capturing from a viewpoint other than the base viewpoint is to be coded, the identical viewpoint image and an image captured from an adjacent viewpoint that is nearer to the base viewpoint (hereinafter referred to as an adjacent viewpoint image) are used as the reference images.
Japanese Patent Application Laid-Open No. 9-0261653 discusses performing the inter-viewpoint prediction employing the identical viewpoint image and the adjacent viewpoint image as candidates for the reference images. As a result, if imaging conditions are different, a prediction error in the inter-viewpoint prediction increases, and coding efficiency decreases even when the reference image is the identical viewpoint image or the adjacent image. Further, if an image in which there is underexposure or overexposure is used as the base viewpoint, the coding efficiency is similarly reduced.